SUMI being tested by Marshall engineer's at the National Space Science and Technology Center high bay. SUMI is slated to launch on a sounding rocket from White Sands Missile Range, N.M., on July 5. This advanced instrument, built by a team of Marshall solar physicists and engineers, measures the strength and direction of magnetic fields in the transition region. (Janet Anderson)View large image

How much do you know about the sun? It's hot, round and powers all life on Earth. Pretty impressive! But exactly how the sun's energy ripples, churns and flows out into the solar system remains a mystery. That's why a team of solar physicists and engineers at NASA's Marshall Space Flight Center in Huntsville, Ala., are launching the Solar Ultraviolet Magnetograph Investigation, or SUMI, for a second time. SUMI is an experimental instrument designed to take unprecedented measurements of the sun's output, providing researchers with new, better understanding of the sun's ever-changing magnetic field activity.

SUMI is slated to launch on a sounding rocket from White Sands Missile Range, N.M., on July 5. This advanced instrument, built by a team of Marshall solar physicists and engineers, measures the strength and direction of magnetic fields in the transition region.

The first SUMI launch took place in July 2010. That mission successfully targeted a sun spot and measured the ultraviolet light emitted by magnesium and carbon ions caught in the magnetic fields of the transition region - the layer which lies between the sun's surface, or photosphere, and the corona. This transition region is where accelerated particles from solar flares erupt and can blast their way toward Earth, potentially overloading ground circuits and impacting life on Earth and in space. Such outbursts seriously impact humanity's ability to expand into space, so understanding and predicting them is critically important.

"We're flying SUMI on a sounding rocket for a second time to refine technology and make adjustments to instruments and their measuring capabilities," said Jonathan Cirtain, Principal Investigator and heliophysicist at the Marshall center. "If we're successful, future satellite missions to study the sun can incorporate our technology and hopefully help complete the picture of how the sun's energy transfer mechanisms really work."

SUMI, part telescope and part spectrograph, is designed to capture information from the transition region, which is impossible to see from the ground. For an instrument that is just 22 inches across and 10 feet long, SUMI is basically a complex telescope that images the sun. A small slit allows a beam of light from the sun to pass into the body of the instrument. The light then encounters an intricate device called a wave plate that works like polarized sunglasses to filter the light. As the wave plate rotates, it allows different polarizations of light through. The strength of that polarization is proportional to the direction and strength of the magnetic field.

In the corona, where the gas pressure is lower, the magnetic field drives the dynamics of the atmosphere. Scientists are not quite sure what happens in the transition layer, where gas dominance is believed to give way to that magnetic field dominance. SUMI's specialized optical components were developed specifically to make exploratory measurements in this region.

During its brief sounding rocket flight, which will carry the instrument 125-185 miles into Earth's atmosphere, SUMI will collect just five minutes worth of data. Employing a technology similar to that used in polarized sunglasses, SUMI will determine the intensity of emission for multiple degrees of polarization. This will permit characterization of the strength and direction of the magnetic field at several altitudes in the solar atmosphere, as the degree of polarization for the emission source is dependent on the direction and strength of the field.